A battery includes a separator to electrically separate a cathode and an anode. The separator separates electrodes (i.e., the cathode and anode) from each other and allows ions within the battery to flow through the separator. Accordingly, the separator prevents a short-circuit that can be resulted from a direct electronic contact between the cathode and the anode. Further, the separator affects the internal resistance, stability, cycle-life, operating temperature, and kinetic parameters such as discharge and charge rates of the battery according to the structural and physiochemical properties of the separator.